1. Field of the Invention
This invention relates to a control system for a vehicle including an electric throttle control device for electrically controlling a throttle valve, and an automatic transmission, and more particularly to a control system for controlling the vehicle when the electric throttle control device is in a condition incapable of controlling the throttle valve.
2. Description of the Prior Art
Conventionally, a vehicle control system of the above kind has been disclosed e.g. in the Publication of Japanese Patent No. 2891019. According to the vehicle control system, when a throttle valve has become uncontrollable e.g. due to an electrical or mechanical failure of an electric throttle control device, the electric throttle control device is deenergized, and at the same time the throttle valve is held at a default opening position so as to avoid an engine stall and allow the vehicle to travel only to find a nearby place to park.
Further, in the vehicle control system, when the throttle valve is uncontrollable, a highest allowable speed position of an automatic transmission is determined based on an operation amount or stepping amount of an accelerator pedal, and a speed position at which a largest driving force can be obtained is selected from among the determined highest speed position and speed positions lower than this so as to ensure the largest driving force according to a driver""s intention to accelerate.
As described above, in the above vehicle control system, when the throttle valve has become uncontrollable due to a failure of the electric throttle control device, a proper speed position of the automatic transmission is selected or determined based on the operation amount or stepping amount of the accelerator pedal to control the automatic transmission such that the largest driving force can be obtained. For this reason, e.g. when the accelerator pedal is stepped on by the driver for acceleration of the vehicle, the speed position is down-shifted so as to obtain the largest driving force, and hence the speed of the vehicle is reduced suddenly by engine brake, which makes it impossible for the vehicle to smoothly travel only to find a nearby place to park, causing degradation of drivability.
It is an object of the invention to provide a control system for a vehicle, which enables the vehicle to travel only to find a nearby place to park when an electric throttle control device becomes incapable of controlling a throttle valve, thereby improving drivability.
To attain the above object, according to a first aspect of the present invention, there is provided a control system for a vehicle including an electric throttle control device for electrically controlling a throttle valve that controls an amount of intake air to be supplied to an internal combustion engine, and an automatic transmission,
the control system comprising:
uncontrollability-determining means for determining whether or not the electric throttle control device is in a condition incapable of controlling the throttle valve;
energization-interrupting means for interrupting energization of the electric throttle control device when it is determined by the uncontrollability-determining means that the electric throttle control device is in the condition incapable of controlling the throttle valve;
opening-holding means for holding the throttle valve at a default opening position when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve;
throttle opening-detecting means for detecting a degree of opening of the throttle valve; and
automatic transmission control means for controlling a speed position of the automatic transmission to a highest speed position if the detected degree of opening of the throttle valve is equal to or smaller than a predetermined reference value when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to this control system, when it is determined that the electric throttle control device is in the condition incapable of controlling the throttle valve, first, energization of the electric throttle control device is interrupted to stop control of the throttle valve by the electric throttle control device. At the same time, the throttle valve is held at the default opening position by the opening-holding means to supply intake air in an amount enabling the vehicle to perform travel to find a nearby place to park, thereby enabling the vehicle to perform this travel. Hereinafter, this travel carried out in case of uncontrollability of the throttle valve will be referred to as xe2x80x9crefuge runningxe2x80x9d. Further, when the detected degree of opening of the throttle valve is equal to or smaller than a predetermined reference value, the speed position of the automatic transmission is forcibly controlled to the highest speed position by the automatic transmission control means. Therefore, even when the accelerator pedal of the vehicle is stepped on during actual refuge running, downshift of the speed position is prevented, and hence it is possible to positively avoid a sudden decrease in the vehicle speed by engine brake, thereby achieving smooth refuge running.
Preferably, the control system further comprises vehicle speed-detecting means for detecting a traveling speed of the vehicle, and the automatic transmission control means controls the speed position of the automatic transmission to the highest speed position if the detected vehicle speed is equal to or higher than a predetermined reference value when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to this preferred embodiment, the speed position of the automatic transmission is also controlled to the highest speed position when the detected vehicle speed is equal to or higher than the predetermined reference value. In general, when vehicle speed is high, a driver is apt to feel deceleration by engine brake. This preferred embodiment makes it possible to positively prevent the driver from having such feeling and achieve smooth refuge running.
To attain the above object, according to a second aspect of the invention, there is provided a control system for a vehicle including an electric throttle control device for electrically controlling a throttle valve that controls an amount of intake air to be supplied to an internal combustion engine, and an automatic transmission,
the control system comprising:
an uncontrollability-determining module for determining whether or not the electric throttle control device is in a condition incapable of controlling the throttle valve;
an energization-interrupting module for interrupting energization of the electric throttle control device when it is determined by the uncontrollability-determining module that the electric throttle control device is in the condition incapable of controlling the throttle valve;
an opening-holding module for holding the throttle valve at a default opening position when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve;
a throttle opening-detecting module for detecting a degree of opening of the throttle valve; and
an automatic transmission control module for controlling a speed position of the automatic transmission to a highest speed position if the detected degree of opening of the throttle valve is equal to or smaller than a predetermined reference value when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to the second aspect of the invention, the same advantageous effects as provided by the first aspect of the invention can be obtained.
Preferably, the control system further comprises a vehicle speed-detecting module for detecting a traveling speed of the vehicle, and the automatic transmission control module controls the speed position of the automatic transmission to the highest speed position if the detected vehicle speed is equal to or higher than a predetermined reference value when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to this preferred embodiment, the same advantageous effects as provided by the preferred embodiment of the first aspect of the invention can be obtained.
To attain the above object, according to a third aspect of the invention, there is provided a control method of controlling a vehicle including an electric throttle control device for electrically controlling a throttle valve that controls an amount of intake air to be supplied to an internal combustion engine, and an automatic transmission,
the control method comprising the steps of:
determining whether or not the electric throttle control device is in a condition incapable of controlling the throttle valve;
interrupting energization of the electric throttle control device when it is determined that the electric throttle control device is in the condition incapable of controlling the throttle valve;
holding the throttle valve at a default opening position when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve;
detecting a degree of opening of the throttle valve; and
controlling a speed position of the automatic transmission to a highest speed position if the detected degree of opening of the throttle valve is equal to or smaller than a predetermined reference value when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to the third aspect of the invention, the same advantageous effects as provided by the first aspect of the invention can be obtained.
Preferably, the control method further comprises the step of detecting a traveling speed of the vehicle, and the step of controlling the speed position of the automatic transmission includes controlling the speed position of the automatic transmission to the highest speed position if the detected vehicle speed is equal to or higher than a predetermined reference value when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to this preferred embodiment, the same advantageous effects as provided by the preferred embodiment of the first aspect of the invention can be obtained.
To attain the above object, according to a fourth aspect of the invention, there is provided an engine control unit including a control program for causing a computer to control a vehicle including an electric throttle control device for electrically controlling a throttle valve that controls an amount of intake air to be supplied to an internal combustion engine, and an automatic transmission, wherein the control program causes the computer to determine whether or not the electric throttle control device is in a condition incapable of controlling the throttle valve, interrupt energization of the electric throttle control device when it is determined that the electric throttle control device is in the condition incapable of controlling the throttle valve, hold the throttle valve at a default opening position when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve, detect a degree of opening of the throttle valve, and control a speed position of the automatic transmission to a highest speed position if the detected degree of opening of the throttle valve is equal to or smaller than a predetermined reference value when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve.
According to the fourth aspect of the invention, the same advantageous effects as provided by the first aspect of the invention can be obtained.
Preferably, the program causes the computer to detect a traveling speed of the vehicle, and the program causes the computer to control the speed position of the automatic transmission to the highest speed position when the electric throttle control device is determined to be in the condition incapable of controlling the throttle valve, further on condition that the detected vehicle speed is equal to or higher than a predetermined reference value.
According to this preferred embodiment, the same advantageous effects as provided by the preferred embodiment of the first aspect of the invention can be obtained.
The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.